1
|
Lancaster MS, Graham BH. Succinyl-CoA Synthetase Dysfunction as a Mechanism of Mitochondrial Encephalomyopathy: More than Just an Oxidative Energy Deficit. Int J Mol Sci 2023; 24:10725. [PMID: 37445899 PMCID: PMC10342173 DOI: 10.3390/ijms241310725] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 06/23/2023] [Accepted: 06/25/2023] [Indexed: 07/15/2023] Open
Abstract
Biallelic pathogenic variants in subunits of succinyl-CoA synthetase (SCS), a tricarboxylic acid (TCA) cycle enzyme, are associated with mitochondrial encephalomyopathy in humans. SCS catalyzes the interconversion of succinyl-CoA to succinate, coupled to substrate-level phosphorylation of either ADP or GDP, within the TCA cycle. SCS-deficient encephalomyopathy typically presents in infancy and early childhood, with many patients succumbing to the disease during childhood. Common symptoms include abnormal brain MRI, basal ganglia lesions and cerebral atrophy, severe hypotonia, dystonia, progressive psychomotor regression, and growth deficits. Although subunits of SCS were first identified as causal genes for progressive metabolic encephalomyopathy in the early 2000s, recent investigations are now beginning to unravel the pathomechanisms underlying this metabolic disorder. This article reviews the current understanding of SCS function within and outside the TCA cycle as it relates to the complex and multifactorial mechanisms underlying SCS-related mitochondrial encephalomyopathy.
Collapse
Affiliation(s)
| | - Brett H. Graham
- Department of Medical & Molecular Genetics, Indiana University School of Medicine, 975 W. Walnut St., Room IB257, Indianapolis, IN 46202, USA;
| |
Collapse
|
2
|
Wang H, Han Y, Li S, Chen Y, Chen Y, Wang J, Zhang Y, Zhang Y, Wang J, Xia Y, Yuan J. Mitochondrial DNA Depletion Syndrome and Its Associated Cardiac Disease. Front Cardiovasc Med 2022; 8:808115. [PMID: 35237671 PMCID: PMC8882844 DOI: 10.3389/fcvm.2021.808115] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2021] [Accepted: 12/23/2021] [Indexed: 12/06/2022] Open
Abstract
Mitochondria is a ubiquitous, energy-supplying (ATP-based) organelle found in nearly all eukaryotes. It acts as a “power plant” by producing ATP through oxidative phosphorylation, providing energy for the cell. The bioenergetic functions of mitochondria are regulated by nuclear genes (nDNA). Mitochondrial DNA (mtDNA) and respiratory enzymes lose normal structure and function when nuclear genes encoding the related mitochondrial factors are impaired, resulting in deficiency in energy production. Massive generation of reactive oxygen species and calcium overload are common causes of mitochondrial diseases. The mitochondrial depletion syndrome (MDS) is associated with the mutations of mitochondrial genes in the nucleus. It is a heterogeneous group of progressive disorders characterized by the low mtDNA copy number. TK2, FBXL4, TYPM, and AGK are genes known to be related to MDS. More recent studies identified new mutation loci associated with this disease. Herein, we first summarize the structure and function of mitochondria, and then discuss the characteristics of various types of MDS and its association with cardiac diseases.
Collapse
Affiliation(s)
- Haiying Wang
- Department of Physiology, Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yijun Han
- Clinical Medical College, Jining Medical University, Jining, China
| | - Shenwei Li
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yunan Chen
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yafen Chen
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Jing Wang
- Dongying Fifth People's Hospital, Dongying, China
| | - Yuqing Zhang
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yawen Zhang
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Jingsuo Wang
- Institute of Basic Medical College, Jining Medical University, Jining, China
| | - Yong Xia
- Key Laboratory of Precision Oncology of Shandong Higher Education, Institute of Precision Medicine, Jining Medical University, Jining, China
- Yong Xia
| | - Jinxiang Yuan
- The Collaborative Innovation Center, Jining Medical University, Jining, China
- *Correspondence: Jinxiang Yuan
| |
Collapse
|
3
|
Preferent Diaphragmatic Involvement in TK2 Deficiency: An Autopsy Case Study. Int J Mol Sci 2021; 22:ijms22115598. [PMID: 34070501 PMCID: PMC8199166 DOI: 10.3390/ijms22115598] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2021] [Revised: 05/18/2021] [Accepted: 05/20/2021] [Indexed: 12/23/2022] Open
Abstract
Our goal was to analyze postmortem tissues of an adult patient with late-onset thymidine kinase 2 (TK2) deficiency who died of respiratory failure. Compared with control tissues, we found a low mtDNA content in the patient’s skeletal muscle, liver, kidney, small intestine, and particularly in the diaphragm, whereas heart and brain tissue showed normal mtDNA levels. mtDNA deletions were present in skeletal muscle and diaphragm. All tissues showed a low content of OXPHOS subunits, and this was especially evident in diaphragm, which also exhibited an abnormal protein profile, expression of non-muscular β-actin and loss of GAPDH and α-actin. MALDI-TOF/TOF mass spectrometry analysis demonstrated the loss of the enzyme fructose-bisphosphate aldolase, and enrichment for serum albumin in the patient’s diaphragm tissue. The TK2-deficient patient’s diaphragm showed a more profound loss of OXPHOS proteins, with lower levels of catalase, peroxiredoxin 6, cytosolic superoxide dismutase, p62 and the catalytic subunits of proteasome than diaphragms of ventilated controls. Strong overexpression of TK1 was observed in all tissues of the patient with diaphragm showing the highest levels. TK2 deficiency induces a more profound dysfunction of the diaphragm than of other tissues, which manifests as loss of OXPHOS and glycolytic proteins, sarcomeric components, antioxidants and overactivation of the TK1 salvage pathway that is not attributed to mechanical ventilation.
Collapse
|
4
|
Liu Y, Wu W, Huang Q. Endoscopic management of pediatric extubation failure in the intensive care unit. Int J Pediatr Otorhinolaryngol 2020; 139:110465. [PMID: 33120102 DOI: 10.1016/j.ijporl.2020.110465] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/10/2020] [Revised: 10/20/2020] [Accepted: 10/20/2020] [Indexed: 11/29/2022]
Abstract
OBJECTIVES This study investigated the endoscopic findings associated with pediatric extubation failure (EF) and evaluated the prognosis of endoscopic procedures. METHODS We retrospectively reviewed the data of children with EF in the intensive care unit from January 1, 2013 to December 31, 2019. Fifty-one children receiving endoscopic examination were enrolled in this study. EF was defined as the need for reintubation within 72 h of the first attempted extubation. RESULTS Thirty-three children (65%) were successfully extubated after endoscopic procedures, and 18 children (35%) failed in extubation. There was a higher percentage of children transferred from other hospitals with intubation in the failure group (56% vs 12%, p = 0.002). Subglottic stenosis (SGS) (35%) and laryngeal and tracheal granulation (33%) were two of the most common findings. Fourteen patients (82%) with granulation were successfully extubated. Two children in the failure group were diagnosed with mitochondrial myopathies (chrM:3243) and congenital myasthenic syndrome (CHAT). The success rate in cases of SGS reached 83% (15/18). Five patients diagnosed with laryngomalacia and another 3 patients with tracheomalacia failed extubation after supraglottoplasty and needed a temporary tracheostomy. CONCLUSION Granulation and subglottic stenosis were the leading causes of extubation failure. Patients transferred with intubation might have a poor prognosis after endoscopic procedures. Neuromuscular and metabolic disorders could be a hidden reason for extubation failure.
Collapse
Affiliation(s)
- Yupeng Liu
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai, 200092, China; Ear Institute, Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai, 200092, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, 1665 Kongjiang Road, Shanghai, 200092, China.
| | - Wenjin Wu
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai, 200092, China; Ear Institute, Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai, 200092, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, 1665 Kongjiang Road, Shanghai, 200092, China.
| | - Qi Huang
- Department of Otolaryngology Head and Neck Surgery, Xinhua Hospital, Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai, 200092, China; Ear Institute, Shanghai Jiaotong University School of Medicine, 1665 Kongjiang Road, Shanghai, 200092, China; Shanghai Key Laboratory of Translational Medicine on Ear and Nose Diseases, 1665 Kongjiang Road, Shanghai, 200092, China.
| |
Collapse
|
5
|
SUCLG1 mutations and mitochondrial encephalomyopathy: a case study and review of the literature. Mol Biol Rep 2020; 47:9699-9714. [PMID: 33230783 DOI: 10.1007/s11033-020-05999-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2020] [Accepted: 11/11/2020] [Indexed: 10/22/2022]
Abstract
The mitochondrial encephalomyopathies represent a clinically heterogeneous group of neurodegenerative disorders. The clinical phenotype of patients could be explained by mutations of mitochondria-related genes, notably SUCLG1 and SUCLA2. Here, we presented a 5-year-old boy with clinical features of mitochondrial encephalomyopathy from Iran. Also, a systematic review was performed to explore the involvement of SUCLG1 mutations in published mitochondrial encephalomyopathies cases. Genotyping was performed by implementing whole-exome sequencing. Moreover, quantification of the mtDNA content was performed by real-time qPCR. We identified a novel, homozygote missense variant chr2: 84676796 A > T (hg19) in the SUCLG1 gene. This mutation substitutes Cys with Ser at the 60-position of the SUCLG1 protein. Furthermore, the in-silico analysis revealed that the mutated position in the genome is well conserved in mammalians, that implies mutation in this residue would possibly result in phenotypic consequences. Here, we identified a novel, homozygote missense variant chr2: 84676796 A > T in the SUCLG1 gene. Using a range of experimental and in silico analysis, we found that the mutation might explain the observed phenotype in the family.
Collapse
|
6
|
Peralta S, González-Quintana A, Ybarra M, Delmiro A, Pérez-Pérez R, Docampo J, Arenas J, Blázquez A, Ugalde C, Martín MA. Novel ATAD3A recessive mutation associated to fatal cerebellar hypoplasia with multiorgan involvement and mitochondrial structural abnormalities. Mol Genet Metab 2019; 128:452-462. [PMID: 31727539 DOI: 10.1016/j.ymgme.2019.10.012] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/02/2019] [Revised: 10/29/2019] [Accepted: 10/30/2019] [Indexed: 11/24/2022]
Abstract
Lethal neonatal encephalopathies are heterogeneous congenital disorders that can be caused by mitochondrial dysfunction. Biallelic large deletions in the contiguous ATAD3B and ATAD3A genes, encoding mitochondrial inner membrane ATPases of unknown function, as well as compound heterozygous nonsense and missense mutations in the ATAD3A gene have been recently associated with fatal neonatal cerebellar hypoplasia. In this work, whole exome sequencing (WES) identified the novel homozygous variant c.1217 T > G in ATAD3A, predicting a p.(Leu406Arg) substitution, in four siblings from a consanguineous family presenting with fatal neonatal cerebellar hypoplasia, seizures, axial hypotonia, hypertrophic cardiomyopathy, hepatomegaly, congenital cataract, and dysmorphic facies. Biochemical phenotypes of the patients included hyperlactatemia and hypocholesterolemia. Healthy siblings and parents were heterozygous for this variant, which is predicted to introduce a polar chain within the catalytic domain of ATAD3A that shortens its beta-sheet structure, presumably affecting protein stability. Accordingly, patient's fibroblasts with the homozygous variant displayed a specific reduction in ATAD3A protein levels associated with profound ultrastructural alterations of mitochondrial cristae and morphology. Our findings exclude the causative role of ATAD3B on this severe phenotype, expand the phenotypical spectrum of ATAD3A pathogenic variants and emphasize the vital role of ATAD3A in mitochondrial biogenesis.
Collapse
Affiliation(s)
- Susana Peralta
- Laboratorio de Enfermedades Raras, Mitocondriales y Neuromusculares, Instituto de Investigación Hospital 12 de Octubre (i+12), 28041 Madrid, Spain
| | - Adrián González-Quintana
- Laboratorio de Enfermedades Raras, Mitocondriales y Neuromusculares, Instituto de Investigación Hospital 12 de Octubre (i+12), 28041 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, U723, 28029 Madrid, Spain
| | - Marta Ybarra
- Servicio de Neonatología, Hospital Infantil La Paz, 28046 Madrid, Spain
| | - Aitor Delmiro
- Laboratorio de Enfermedades Raras, Mitocondriales y Neuromusculares, Instituto de Investigación Hospital 12 de Octubre (i+12), 28041 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, U723, 28029 Madrid, Spain
| | - Rafael Pérez-Pérez
- Laboratorio de Enfermedades Raras, Mitocondriales y Neuromusculares, Instituto de Investigación Hospital 12 de Octubre (i+12), 28041 Madrid, Spain
| | - Jorge Docampo
- Laboratorio de Enfermedades Raras, Mitocondriales y Neuromusculares, Instituto de Investigación Hospital 12 de Octubre (i+12), 28041 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, U723, 28029 Madrid, Spain
| | - Joaquín Arenas
- Laboratorio de Enfermedades Raras, Mitocondriales y Neuromusculares, Instituto de Investigación Hospital 12 de Octubre (i+12), 28041 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, U723, 28029 Madrid, Spain
| | - Alberto Blázquez
- Laboratorio de Enfermedades Raras, Mitocondriales y Neuromusculares, Instituto de Investigación Hospital 12 de Octubre (i+12), 28041 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, U723, 28029 Madrid, Spain
| | - Cristina Ugalde
- Laboratorio de Enfermedades Raras, Mitocondriales y Neuromusculares, Instituto de Investigación Hospital 12 de Octubre (i+12), 28041 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, U723, 28029 Madrid, Spain.
| | - Miguel A Martín
- Laboratorio de Enfermedades Raras, Mitocondriales y Neuromusculares, Instituto de Investigación Hospital 12 de Octubre (i+12), 28041 Madrid, Spain; Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Instituto de Salud Carlos III, U723, 28029 Madrid, Spain
| |
Collapse
|
7
|
Chinopoulos C, Batzios S, van den Heuvel LP, Rodenburg R, Smeets R, Waterham HR, Turkenburg M, Ruiter JP, Wanders RJA, Doczi J, Horvath G, Dobolyi A, Vargiami E, Wevers RA, Zafeiriou D. Mutated SUCLG1 causes mislocalization of SUCLG2 protein, morphological alterations of mitochondria and an early-onset severe neurometabolic disorder. Mol Genet Metab 2019; 126:43-52. [PMID: 30470562 DOI: 10.1016/j.ymgme.2018.11.009] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/03/2018] [Revised: 11/14/2018] [Accepted: 11/14/2018] [Indexed: 11/19/2022]
Abstract
Succinate-CoA ligase (SUCL) is a heterodimer consisting of an alpha subunit encoded by SUCLG1, and a beta subunit encoded by either SUCLA2 or SUCLG2 catalyzing an ATP- or GTP-forming reaction, respectively, in the mitochondrial matrix. The deficiency of this enzyme represents an encephalomyopathic form of mtDNA depletion syndromes. We describe the fatal clinical course of a female patient with a pathogenic mutation in SUCLG1 (c.626C > A, p.Ala209Glu) heterozygous at the genomic DNA level, but homozygous at the transcriptional level. The patient exhibited early-onset neurometabolic abnormality culminating in severe brain atrophy and dystonia leading to death by the age of 3.5 years. Urine and plasma metabolite profiling was consistent with SUCL deficiency which was confirmed by enzyme analysis and lack of mitochondrial substrate-level phosphorylation (mSLP) in skin fibroblasts. Oxygen consumption- but not extracellular acidification rates were altered only when using glutamine as a substrate, and this was associated with mild mtDNA depletion and no changes in ETC activities. Immunoblot analysis revealed no detectable levels of SUCLG1, while SUCLA2 and SUCLG2 protein expressions were largely reduced. Confocal imaging of triple immunocytochemistry of skin fibroblasts showed that SUCLG2 co-localized only partially with the mitochondrial network which otherwise exhibited an increase in fragmentation compared to control cells. Our results outline the catastrophic consequences of the mutated SUCLG1 leading to strongly reduced SUCL activity, mSLP impairment, mislocalization of SUCLG2, morphological alterations in mitochondria and clinically to a severe neurometabolic disease, but in the absence of changes in mtDNA levels or respiratory complex activities.
Collapse
Affiliation(s)
| | - Spyros Batzios
- 1st Department of Pediatrics, "Hippokratio" General Hospital, Aristotle University, Thessaloniki, Greece; Department of Paediatric Metabolic Medicine, Great Ormond Street Hospital, London, UK
| | - Lambertus P van den Heuvel
- Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands; Translational Metabolic Laboratory, Department Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Richard Rodenburg
- Department of Pediatrics, Radboud University Medical Centre, Nijmegen, The Netherlands; Translational Metabolic Laboratory, Department Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Roel Smeets
- Translational Metabolic Laboratory, Department Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands
| | - Hans R Waterham
- Laboratory Genetic Metabolic Diseases, Amsterdam University Medical Centers, University of Amsterdam, The Netherlands
| | - Marjolein Turkenburg
- Laboratory Genetic Metabolic Diseases, Amsterdam University Medical Centers, University of Amsterdam, The Netherlands
| | - Jos P Ruiter
- Laboratory Genetic Metabolic Diseases, Amsterdam University Medical Centers, University of Amsterdam, The Netherlands
| | - Ronald J A Wanders
- Laboratory Genetic Metabolic Diseases, Amsterdam University Medical Centers, University of Amsterdam, The Netherlands
| | - Judit Doczi
- Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary
| | - Gergo Horvath
- Department of Medical Biochemistry, Semmelweis University, Budapest, Hungary
| | - Arpad Dobolyi
- MTA-ELTE Laboratory of Molecular and Systems Neurobiology, Department of Physiology and Neurobiology, Hungarian Academy of Sciences, Eotvos Lorand University, Budapest, Hungary; Department of Anatomy, Histology and Embryology, Semmelweis University, Budapest, Hungary
| | - Euthymia Vargiami
- 1st Department of Pediatrics, "Hippokratio" General Hospital, Aristotle University, Thessaloniki, Greece
| | - Ron A Wevers
- Translational Metabolic Laboratory, Department Laboratory Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands.
| | - Dimitrios Zafeiriou
- 1st Department of Pediatrics, "Hippokratio" General Hospital, Aristotle University, Thessaloniki, Greece.
| |
Collapse
|
8
|
Maalej M, Tej A, Bouguila J, Tilouche S, Majdoub S, Khabou B, Tabbebi M, Felhi R, Ammar M, Mkaouar-Rebai E, Keskes L, Boughamoura L, Fakhfakh F. Clinical, Molecular, and Computational Analysis in two cases with mitochondrial encephalomyopathy associated with SUCLG1 mutation in a consanguineous family. Biochem Biophys Res Commun 2017; 495:1730-1737. [PMID: 29217198 DOI: 10.1016/j.bbrc.2017.12.011] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2017] [Accepted: 12/02/2017] [Indexed: 11/28/2022]
Abstract
Deficiency of the mitochondrial enzyme succinyl COA ligase (SUCL) is associated with encephalomyopathic mtDNA depletion syndrome and methylmalonic aciduria. This disorder is caused by mutations in both SUCL subunits genes: SUCLG1 (α subnit) and SUCLA2 (β subnit). We report here, two Tunisian patients belonging to a consanguineous family with mitochondrial encephalomyopathy, hearing loss, lactic acidosis, hypotonia, psychomotor retardation and methylmalonic aciduria. Mutational analysis of SUCLG1 gene showed, for the first time, the presence of c.41T > C in the exon 1 at homozygous state. In-silico analysis revealed that this mutation substitutes a conserved methionine residue to a threonine at position 14 (p.M14T) located at the SUCLG1 protein mitochondrial targeting sequence. Moreover, these analysis predicted that this mutation alter stability structure and mitochondrial translocation of the protein. In Addition, a decrease in mtDNA copy number was revealed by real time PCR in the peripheral blood leukocytes in the two patients compared with controls.
Collapse
Affiliation(s)
- Marwa Maalej
- Laboratory of Molecular and Functional Genetics, Faculty of Science of Sfax, University of Sfax, Tunisia; Laboratory of Human Molecular Genetics, Faculty of Medicine of Sfax, University of Sfax, Tunisia.
| | - Amel Tej
- Service de pédiatrie, C.H.U. Farhat Hachad de sousse, University of Sousse, Tunisia
| | - Jihène Bouguila
- Service de pédiatrie, C.H.U. Farhat Hachad de sousse, University of Sousse, Tunisia
| | - Samia Tilouche
- Service de pédiatrie, C.H.U. Farhat Hachad de sousse, University of Sousse, Tunisia
| | - Senda Majdoub
- Service de Radiologie, CHU Farhat Hached, Sousse, University of Sousse, Tunisia
| | - Boudour Khabou
- Laboratory of Human Molecular Genetics, Faculty of Medicine of Sfax, University of Sfax, Tunisia
| | - Mouna Tabbebi
- Laboratory of Human Molecular Genetics, Faculty of Medicine of Sfax, University of Sfax, Tunisia
| | - Rahma Felhi
- Laboratory of Molecular and Functional Genetics, Faculty of Science of Sfax, University of Sfax, Tunisia
| | - Marwa Ammar
- Laboratory of Molecular and Functional Genetics, Faculty of Science of Sfax, University of Sfax, Tunisia
| | - Emna Mkaouar-Rebai
- Laboratory of Molecular and Functional Genetics, Faculty of Science of Sfax, University of Sfax, Tunisia
| | - Leila Keskes
- Laboratory of Human Molecular Genetics, Faculty of Medicine of Sfax, University of Sfax, Tunisia
| | - Lamia Boughamoura
- Service de pédiatrie, C.H.U. Farhat Hachad de sousse, University of Sousse, Tunisia
| | - Faiza Fakhfakh
- Laboratory of Molecular and Functional Genetics, Faculty of Science of Sfax, University of Sfax, Tunisia.
| |
Collapse
|
9
|
Zhou Y, Yi J, Liu L, Wang X, Dong L, Du A. Acute mitochondrial myopathy with respiratory insufficiency and motor axonal polyneuropathy. Int J Neurosci 2017; 128:231-236. [PMID: 28969510 DOI: 10.1080/00207454.2017.1387113] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
BACKGROUND Mitochondrial myopathies (MMs) are mainly presented with chronic muscle weakness and accompanied with other syndromes. MM with acute respiratory insufficiency is rare. AIMS To reveal the clinical, pathological and molecular characteristics of a life-threatening MM. METHODS Muscle biopsy and enzyme staining were performed in skeletal muscles. Mitochondrial DNA (mtDNA) sequencing was analyzed and heteroplasmy were quantified by pyrosequencing. RESULTS All three patients had tachycardia, acute lactic acidosis, dyspnea and sudden severe muscle weakness. Two patients had calf edema and abdominal pain, and one had a heart attack. Electromyography in two patients showed dramatically decreased axonal amplitudes of motor nerves. Muscle biopsies showed ragged red fibers and dramatic mitochondrial abnormality. A mtDNA m.3243A>G mutation was identified in Patient 1 (mutation load: 29% in blood and 73% in muscle) and Patient 3 (79% in blood and 89% in muscle). A mtDNA m.8344A>G mutation was found in Patient 2 (mutation load 80.4% in blood). CONCLUSION MM characterized by lactic acidosis, respiratory failure and acute motor axonal neuropathy is life threatening.
Collapse
Affiliation(s)
- Ying Zhou
- a Department of Cardiology , Second Affiliated Hospital, Zhejiang University School of Medicine , Hangzhou , China
| | - Jianhua Yi
- b Department of Emergency Medicine , Second Affiliated Hospital, Zhejiang University School of Medicine , Hangzhou , China
| | - Li Liu
- c Mitochondrial Disease Research Center, Institute of Genetics , College of Life Science, Zhejiang University , Hangzhou , China
| | - Xiaoping Wang
- d Department of Neurology , Tongren Hospital, Shanghai Jiaotong University School of Medicine , Shanghai , China
| | - Liang Dong
- a Department of Cardiology , Second Affiliated Hospital, Zhejiang University School of Medicine , Hangzhou , China
| | - Ailian Du
- d Department of Neurology , Tongren Hospital, Shanghai Jiaotong University School of Medicine , Shanghai , China
| |
Collapse
|
10
|
Donti TR, Masand R, Scott DA, Craigen WJ, Graham BH. Expanding the phenotypic spectrum of Succinyl-CoA ligase deficiency through functional validation of a new SUCLG1 variant. Mol Genet Metab 2016; 119:68-74. [PMID: 27484306 PMCID: PMC5031536 DOI: 10.1016/j.ymgme.2016.07.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/18/2016] [Revised: 07/17/2016] [Accepted: 07/18/2016] [Indexed: 11/21/2022]
Abstract
Deficiency of the TCA cycle enzyme Succinyl-CoA Synthetase/Ligase (SCS), due to pathogenic variants in subunits encoded by SUCLG1 and SUCLA2, causes mitochondrial encephalomyopathy, methylmalonic acidemia, and mitochondrial DNA (mtDNA) depletion. In this study, we report an 11year old patient who presented with truncal ataxia, chorea, hypotonia, bilateral sensorineural hearing loss and preserved cognition. Whole exome sequencing identified a heterozygous known pathogenic variant and a heterozygous novel missense variant of uncertain clinical significance (VUS) in SUCLG1. To validate the suspected pathogenicity of the novel VUS, molecular and biochemical analyses were performed using primary skin fibroblasts from the patient. The patient's cells lack the SUCLG1 protein, with significantly reduced levels of SUCLA2 and SUCLG2 protein. This leads to essentially undetectable SCS enzyme activity, mtDNA depletion, and cellular respiration defects. These abnormal phenotypes are rescued upon ectopic expression of wild-type SUCLG1 in the patient's fibroblasts, thus functionally confirming the pathogenic nature of the SUCLG1 VUS identified in this patient and expanding the phenotypic spectrum for SUCLG1 deficiency.
Collapse
Affiliation(s)
- Taraka R Donti
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Ruchi Masand
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Daryl A Scott
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA; Department of Molecular Physiology and Biophysics, Baylor College of Medicine, Houston, TX, USA
| | - William J Craigen
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Brett H Graham
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA.
| |
Collapse
|
11
|
Carrozzo R, Verrigni D, Rasmussen M, de Coo R, Amartino H, Bianchi M, Buhas D, Mesli S, Naess K, Born AP, Woldseth B, Prontera P, Batbayli M, Ravn K, Joensen F, Cordelli DM, Santorelli FM, Tulinius M, Darin N, Duno M, Jouvencel P, Burlina A, Stangoni G, Bertini E, Redonnet-Vernhet I, Wibrand F, Dionisi-Vici C, Uusimaa J, Vieira P, Osorio AN, McFarland R, Taylor RW, Holme E, Ostergaard E. Succinate-CoA ligase deficiency due to mutations in SUCLA2 and SUCLG1: phenotype and genotype correlations in 71 patients. J Inherit Metab Dis 2016; 39:243-52. [PMID: 26475597 DOI: 10.1007/s10545-015-9894-9] [Citation(s) in RCA: 60] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/03/2015] [Revised: 09/04/2015] [Accepted: 09/08/2015] [Indexed: 11/28/2022]
Abstract
BACKGROUND The encephalomyopathic mtDNA depletion syndrome with methylmalonic aciduria is associated with deficiency of succinate-CoA ligase, caused by mutations in SUCLA2 or SUCLG1. We report here 25 new patients with succinate-CoA ligase deficiency, and review the clinical and molecular findings in these and 46 previously reported patients. PATIENTS AND RESULTS Of the 71 patients, 50 had SUCLA2 mutations and 21 had SUCLG1 mutations. In the newly-reported 20 SUCLA2 patients we found 16 different mutations, of which nine were novel: two large gene deletions, a 1 bp duplication, two 1 bp deletions, a 3 bp insertion, a nonsense mutation and two missense mutations. In the newly-reported SUCLG1 patients, five missense mutations were identified, of which two were novel. The median onset of symptoms was two months for patients with SUCLA2 mutations and at birth for SUCLG1 patients. Median survival was 20 years for SUCLA2 and 20 months for SUCLG1. Notable clinical differences between the two groups were hepatopathy, found in 38% of SUCLG1 cases but not in SUCLA2 cases, and hypertrophic cardiomyopathy which was not reported in SUCLA2 patients, but documented in 14% of cases with SUCLG1 mutations. Long survival, to age 20 years or older, was reported in 12% of SUCLA2 and in 10% of SUCLG1 patients. The most frequent abnormality on neuroimaging was basal ganglia involvement, found in 69% of SUCLA2 and 80% of SUCLG1 patients. Analysis of respiratory chain enzyme activities in muscle generally showed a combined deficiency of complexes I and IV, but normal histological and biochemical findings in muscle did not preclude a diagnosis of succinate-CoA ligase deficiency. In five patients, the urinary excretion of methylmalonic acid was only marginally elevated, whereas elevated plasma methylmalonic acid was consistently found. CONCLUSIONS To our knowledge, this is the largest study of patients with SUCLA2 and SUCLG1 deficiency. The most important findings were a significantly longer survival in patients with SUCLA2 mutations compared to SUCLG1 mutations and a trend towards longer survival in patients with missense mutations compared to loss-of-function mutations. Hypertrophic cardiomyopathy and liver involvement was exclusively found in patients with SUCLG1 mutations, whereas epilepsy was much more frequent in patients with SUCLA2 mutations compared to patients with SUCLG1 mutations. The mutation analysis revealed a number of novel mutations, including a homozygous deletion of the entire SUCLA2 gene, and we found evidence of two founder mutations in the Scandinavian population, in addition to the known SUCLA2 founder mutation in the Faroe Islands.
Collapse
Affiliation(s)
- Rosalba Carrozzo
- Unit of Muscular and Neurodegenerative Diseases, Laboratory of Molecular Medicine, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Daniela Verrigni
- Unit of Muscular and Neurodegenerative Diseases, Laboratory of Molecular Medicine, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Magnhild Rasmussen
- Department of Clinical Neurosciences for Children, Oslo University Hospital, Oslo, Norway
| | - Rene de Coo
- Department of Neurology, Erasmus Medical Centre, Rotterdam, The Netherlands
| | - Hernan Amartino
- Servicio de Neurología Infantil, Hospital Universitario Austral, Buenos Aires, Argentina
| | - Marzia Bianchi
- Unit of Muscular and Neurodegenerative Diseases, Laboratory of Molecular Medicine, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Daniela Buhas
- Department of Medical Genetics, Montreal Children's Hospital, Montréal, Quebéc, Canada
| | - Samir Mesli
- Biochemistry, CHU de Bordeaux, Bordeaux, France
| | - Karin Naess
- Department of Laboratory Medicine and Centre for Inherited Metabolic Diseases, Karolinska Institutet and Karolinska University Hospital, Stockholm, Sweden
| | - Alfred Peter Born
- Department of Pediatrics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Berit Woldseth
- Department of Medical Biochemistry, Oslo University Hospital, Oslo, Norway
| | - Paolo Prontera
- Centro di Riferimento Regionale di Genetica Medica, Azienda Ospedaliera di Perugia, CREO, Perugia, Italy
| | - Mustafa Batbayli
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Kirstine Ravn
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Fróði Joensen
- Department of Pediatrics, National Hospital of the Faroe Islands, Tórshavn, Faroe Islands
| | - Duccio M Cordelli
- U.O. Neuropsichiatria Infantile - Franzoni, Policlinico S. Orsola Malpighi, Bologna, Italy
| | | | - Mar Tulinius
- Department of Pediatrics, University of Gothenburg, The Queen Silvia's Children Hospital, Gothenburg, Sweden
| | - Niklas Darin
- Department of Pediatrics, University of Gothenburg, The Queen Silvia's Children Hospital, Gothenburg, Sweden
| | - Morten Duno
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Philippe Jouvencel
- Neonatal and Pediatric Intensive Care Unit, Children's Hospital, Bordeaux, France
| | - Alberto Burlina
- Division of Inherited Metabolic Diseases, Department of Pediatrics, University Hospital of Padua, Padua, Italy
| | - Gabriela Stangoni
- Centro di Riferimento Regionale di Genetica Medica, Azienda Ospedaliera di Perugia, CREO, Perugia, Italy
| | - Enrico Bertini
- Unit of Muscular and Neurodegenerative Diseases, Laboratory of Molecular Medicine, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | | | - Flemming Wibrand
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark
| | - Carlo Dionisi-Vici
- Division of Metabolism, Bambino Gesù Children's Hospital, IRCCS, Rome, Italy
| | - Johanna Uusimaa
- Institute of Clinical Medicine/Department of Paediatrics, Finland and Medical Research Center, University of Oulu, Oulu University Hospital, Oulu, Finland
| | - Paivi Vieira
- Institute of Clinical Medicine/Department of Paediatrics, Finland and Medical Research Center, University of Oulu, Oulu University Hospital, Oulu, Finland
| | - Andrés Nascimento Osorio
- Unidad de patología neuromuscular, Servicio de Neurología, Hospital Sant Joan de Déu. Hospital Sant Joan de Déu and CIBERER, ISCIII, Barcelona, Spain
| | - Robert McFarland
- Wellcome Trust Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Robert W Taylor
- Wellcome Trust Centre for Mitochondrial Research, Newcastle University, Newcastle upon Tyne, UK
| | - Elisabeth Holme
- Department of Clinical Chemistry, Institute of Biomedicine, The Sahlgrenska Academy at the University of Gothenburg, Gothenburg, Sweden
| | - Elsebet Ostergaard
- Department of Clinical Genetics, Copenhagen University Hospital Rigshospitalet, Copenhagen, Denmark.
| |
Collapse
|
12
|
Liu Y, Li X, Wang Q, Ding Y, Song J, Yang Y. Five novel SUCLG1 mutations in three Chinese patients with succinate-CoA ligase deficiency noticed by mild methylmalonic aciduria. Brain Dev 2016; 38:61-7. [PMID: 26028457 DOI: 10.1016/j.braindev.2015.05.002] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2014] [Revised: 05/02/2015] [Accepted: 05/07/2015] [Indexed: 01/28/2023]
Abstract
OBJECTIVE Methylmalonic aciduria is the most common organic aciduria in mainland China. Succinate-CoA ligase deficiency causes encephalomyopathy with mitochondrial DNA depletion and mild methylmalonic aciduria. Patients usually present with severe encephalomyopathy, infantile lactic acidosis, which can be fatal, and mild methylmalonic aciduria. PATIENTS AND METHODS Three Chinese patients (two boys and one girl) were hospitalized because of severe encephalomyopathy between 7 and 9 months. They presented with severe psychomotor retardation, hypotonia, dystonia, athetoid movements, seizures, feeding problems and failure to thrive. Mild elevated urine methylmalonic acid and blood propionylcarnitine indicated methylmalonic aciduria. Gene capture and high-throughput genomic sequencing was carried out. RESULTS Five novel mutations in SUCLG1 were identified in these patients: c.550G>A (p.G184S) in exon 5, c.751C>T (p.G251S) in exon 7, c.809A>C (p.L270W) in exon 7, c.961C>G (p.A321P) in exon 8 and c.826-2A>G (Splicing) in exon 9. Significant depletion of mtDNA was not observed in the peripheral leukocytes of the three patients in spite of mild decreasing of mitochondrial respiratory chain complex I in two patients and complex V in one patient. After treatment with cobalamin, calcium folinate, L-carnitine, vitamin B1, C, and coenzyme Q10, and nutrition intervention, the patients improved. CONCLUSIONS Succinate-CoA ligase deficiency due to SUCLG1 mutations is a rare cause of methylmalonic aciduria. Biochemical and gene studies are keys for the differential diagnoses. Three Chinese patients with mild methylmalonic aciduria were genetically diagnosed using high-throughput genomic sequencing. Five novel pathogenic mutations in SUCLG1 were identified.
Collapse
Affiliation(s)
- Yupeng Liu
- Peking University First Hospital, Beijing 100034, China
| | - Xiyuan Li
- Peking University First Hospital, Beijing 100034, China
| | - Qiao Wang
- Peking University First Hospital, Beijing 100034, China
| | - Yuan Ding
- Peking University First Hospital, Beijing 100034, China
| | - Jinqing Song
- Peking University First Hospital, Beijing 100034, China
| | - Yanling Yang
- Peking University First Hospital, Beijing 100034, China.
| |
Collapse
|
13
|
Landsverk ML, Zhang VW, Wong LJC, Andersson HC. A SUCLG1 mutation in a patient with mitochondrial DNA depletion and congenital anomalies. Mol Genet Metab Rep 2014; 1:451-454. [PMID: 27896121 PMCID: PMC5121340 DOI: 10.1016/j.ymgmr.2014.09.007] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2014] [Revised: 09/25/2014] [Accepted: 09/25/2014] [Indexed: 02/05/2023] Open
Abstract
Defects in two subunits of succinate-CoA ligase encoded by the genes SUCLG1 and SUCLA2 have been identified in mitochondrial DNA (mtDNA) depletion syndromes. Patients generally present with encephalomyopathy and mild methylmalonic acidemia (MMA), however mutations in SUCLG1 normally appear to result in a more severe clinical phenotype. In this report, we describe a patient with fatal infantile lactic acidosis and multiple congenital anomalies (MCAs) including renal and cardiac defects. Molecular studies showed a defective electron transport chain (ETC), mtDNA depletion, and a novel homozygous mutation in the SUCLG1 gene. Although our patient's clinical biochemical phenotype is consistent with a SUCLG1 mutation, it is unclear whether the MCAs observed in our patient are a result of the SUCLG1 mutation or alterations in a second gene. An increasing number of reports have described MCAs associated with mitochondrial disorders and SUCLG1 specifically. Additional studies such as whole exome sequencing will further define whether additional genes are responsible for the observed MCAs.
Collapse
Affiliation(s)
- Megan L Landsverk
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA; Sanford Health, Sioux Falls, SD, USA
| | - Victor Wei Zhang
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Lee-Jun C Wong
- Department of Molecular and Human Genetics, Baylor College of Medicine, Houston, TX, USA
| | - Hans C Andersson
- Hayward Genetics Center, Tulane University, New Orleans, LA, USA; Department of Pediatrics, Tulane University, New Orleans, LA, USA
| |
Collapse
|
14
|
Morán M, Delmiro A, Blázquez A, Ugalde C, Arenas J, Martín MA. Bulk autophagy, but not mitophagy, is increased in cellular model of mitochondrial disease. BIOCHIMICA ET BIOPHYSICA ACTA 2014; 1842:1059-70. [PMID: 24704045 DOI: 10.1016/j.bbadis.2014.03.013] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/23/2013] [Revised: 03/17/2014] [Accepted: 03/25/2014] [Indexed: 10/25/2022]
Abstract
Oxidative phosphorylation system (OXPHOS) deficiencies are rare diseases but constitute the most frequent inborn errors of metabolism. We analyzed the autophagy route in 11 skin fibroblast cultures derived from patients with well characterized and distinct OXPHOS defects. Mitochondrial membrane potential determination revealed a tendency to decrease in 5 patients' cells but reached statistical significance only in 2 of them. The remaining cells showed either no change or a slight increase in this parameter. Colocalization analysis of mitochondria and autophagosomes failed to show evidence of increased selective elimination of mitochondria but revealed more intense autophagosome staining in patients' fibroblasts compared with controls. Despite the absence of increased mitophagy, Parkin recruitment to mitochondria was detected in both controls' and patients' cells and was slightly higher in cells harboring complex I defects. Western blot analysis of the autophagosome marker LC3B, confirmed significantly higher levels of the protein bound to autophagosomes, LC3B-II, in patients' cells, suggesting an increased bulk autophagy in OXPHOS defective fibroblasts. Inhibition of lysosomal proteases caused significant accumulation of LC3B-II in control cells, whereas in patients' cells this phenomenon was less pronounced. Electron microscopy studies showed higher content of late autophagic vacuoles and lysosomes in OXPHOS defective cells, accompanied by higher levels of the lysosomal marker LAMP-1. Our findings suggest that in OXPHOS deficient fibroblasts autophagic flux could be partially hampered leading to an accumulation of autophagic vacuoles and lysosomes.
Collapse
Affiliation(s)
- María Morán
- Mitochondrial and Neuromuscular Diseases Laboratory, Hospital Universitario 12 de Octubre Research Institute (i+12), Madrid, Spain; Spanish Network for Biomedical Research in Rare Diseases (CIBERER), U723, Spain.
| | - Aitor Delmiro
- Mitochondrial and Neuromuscular Diseases Laboratory, Hospital Universitario 12 de Octubre Research Institute (i+12), Madrid, Spain; Spanish Network for Biomedical Research in Rare Diseases (CIBERER), U723, Spain
| | - Alberto Blázquez
- Mitochondrial and Neuromuscular Diseases Laboratory, Hospital Universitario 12 de Octubre Research Institute (i+12), Madrid, Spain; Spanish Network for Biomedical Research in Rare Diseases (CIBERER), U723, Spain
| | - Cristina Ugalde
- Mitochondrial and Neuromuscular Diseases Laboratory, Hospital Universitario 12 de Octubre Research Institute (i+12), Madrid, Spain; Spanish Network for Biomedical Research in Rare Diseases (CIBERER), U723, Spain
| | - Joaquín Arenas
- Mitochondrial and Neuromuscular Diseases Laboratory, Hospital Universitario 12 de Octubre Research Institute (i+12), Madrid, Spain
| | - Miguel A Martín
- Mitochondrial and Neuromuscular Diseases Laboratory, Hospital Universitario 12 de Octubre Research Institute (i+12), Madrid, Spain; Spanish Network for Biomedical Research in Rare Diseases (CIBERER), U723, Spain
| |
Collapse
|
15
|
Nogueira C, Almeida LS, Nesti C, Pezzini I, Videira A, Vilarinho L, Santorelli FM. Syndromes associated with mitochondrial DNA depletion. Ital J Pediatr 2014; 40:34. [PMID: 24708634 PMCID: PMC3985578 DOI: 10.1186/1824-7288-40-34] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/19/2013] [Accepted: 03/28/2014] [Indexed: 01/21/2023] Open
Abstract
Mitochondrial dysfunction accounts for a large group of inherited metabolic disorders most of which are due to a dysfunctional mitochondrial respiratory chain (MRC) and, consequently, deficient energy production. MRC function depends on the coordinated expression of both nuclear (nDNA) and mitochondrial (mtDNA) genomes. Thus, mitochondrial diseases can be caused by genetic defects in either the mitochondrial or the nuclear genome, or in the cross-talk between the two. This impaired cross-talk gives rise to so-called nuclear-mitochondrial intergenomic communication disorders, which result in loss or instability of the mitochondrial genome and, in turn, impaired maintenance of qualitative and quantitative mtDNA integrity. In children, most MRC disorders are associated with nuclear gene defects rather than alterations in the mtDNA itself. The mitochondrial DNA depletion syndromes (MDSs) are a clinically heterogeneous group of disorders with an autosomal recessive pattern of transmission that have onset in infancy or early childhood and are characterized by a reduced number of copies of mtDNA in affected tissues and organs. The MDSs can be divided into least four clinical presentations: hepatocerebral, myopathic, encephalomyopathic and neurogastrointestinal. The focus of this review is to offer an overview of these syndromes, listing the clinical phenotypes, together with their relative frequency, mutational spectrum, and possible insights for improving diagnostic strategies.
Collapse
Affiliation(s)
| | | | | | | | | | - Laura Vilarinho
- National Institute of Health, Genetics Department, Research and Development Unit, Porto, Portugal.
| | | |
Collapse
|
16
|
Abstract
To highlight differences between early-onset and adult mitochondrial depletion syndromes (MDS) concerning etiology and genetic background, pathogenesis, phenotype, clinical presentation and their outcome. MDSs most frequently occur in neonates, infants, or juveniles and more rarely in adolescents or adults. Mutated genes phenotypically presenting with adult-onset MDS include POLG1, TK2, TyMP, RRM2B, or PEO1/twinkle. Adult MDS manifest similarly to early-onset MDS, as myopathy, encephalo-myopathy, hepato-cerebral syndrome, or with chronic progressive external ophthalmoplegia (CPEO), fatigue, or only minimal muscular manifestations. Diagnostic work-up or treatment is not at variance from early-onset cases. Histological examination of muscle may be normal but biochemical investigations may reveal multiple respiratory chain defects. The outcome appears to be more favorable in adult than in early-onset forms. Mitochondrial depletion syndromes is not only a condition of neonates, infants, or juveniles but rarely also occurs in adults, presenting with minimal manifestations or manifestations like in the early-onset forms. Outcome of adult-onset MDS appears more favorable than early-onset MDS.
Collapse
|
17
|
Woodbridge P, Liang C, Davis RL, Vandebona H, Sue CM. POLG mutations in Australian patients with mitochondrial disease. Intern Med J 2013; 43:150-6. [PMID: 22647225 DOI: 10.1111/j.1445-5994.2012.02847.x] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2012] [Accepted: 05/05/2012] [Indexed: 11/29/2022]
Abstract
BACKGROUND/AIM The nuclear POLG gene encodes the catalytic subunit of DNA polymerase gamma (polγ), the only polymerase involved in the replication and proofreading of mitochondrial DNA. As a consequence, POLG mutations can cause disease through impaired replication of mitochondrial DNA. To date, over 150 different mutations have been identified, with a growing number of associated phenotypes described. The aim of this study was to determine the prevalence of POLG mutations in an adult population of Australian patients with mitochondrial disease, displaying symptoms commonly associated with POLG-related diseases. METHODS The clinical presentations of 322 patients from a specialist adult mitochondrial disease clinic were reviewed. Nineteen exhibited a cluster of three or more predefined clinical manifestations suggestive of POLG-related disease: progressive external ophthalmoplegia, seizures and/or an abnormal electroencephalogram, neuropathy, ataxia, liver function abnormalities, migraine or dysphagia/dysarthria. Patients were screened for mutations by direct nucleotide sequencing of the coding and exon-flanking intronic regions of POLG. RESULTS Five of the 19 patients (26%) displaying a phenotype suggestive of POLG-related disease were found to have informative POLG coding mutations (p.T851A, p.N468D, p.Y831C, p.G517V and novel p.P163S variant). Literature and analysis of these mutations revealed that two of these patients had pathogenic mutations known to cause POLG-related disease (patient #1: p.T851A and p.P163S; patient #2: p.T851A and p.N468D). CONCLUSIONS We conclude that the prevalence of pathogenic POLG mutations in our selected adult Australian cohort with suggestive clinical manifestations was 10%. A further 16% of patients had POLG variants but are unlikely to be responsible for causing their disease.
Collapse
Affiliation(s)
- P Woodbridge
- Department of Neurogenetics, Kolling Institute of Medical Research and University of Sydney, Sydney, Australia
| | | | | | | | | |
Collapse
|
18
|
Rahman S. Gastrointestinal and hepatic manifestations of mitochondrial disorders. J Inherit Metab Dis 2013; 36:659-73. [PMID: 23674168 DOI: 10.1007/s10545-013-9614-2] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/25/2013] [Revised: 04/13/2013] [Accepted: 04/16/2013] [Indexed: 12/23/2022]
Abstract
Inherited defects of oxidative phosphorylation lead to heterogeneous, often multisystem, mitochondrial diseases. This review highlights those mitochondrial syndromes with prominent gastrointestinal and hepatic symptoms, categorised according to underlying disease mechanism. Mitochondrial encephalopathies with major gastrointestinal involvement include mitochondrial neurogastrointestinal encephalopathy and ethylmalonic encephalopathy, which are each associated with highly specific clinical and metabolic profiles. Mitochondrial hepatopathies are most frequently caused by defects of mitochondrial DNA maintenance and expression. Although mitochondrial disorders are notorious for extreme clinical, biochemical and genetic heterogeneity, there are some pathognomonic clinical and metabolic clues that suggest a specific diagnosis, and these are highlighted. An approach to diagnosis of these complex disorders is presented, together with a genetic classification, including mitochondrial DNA disorders and nuclear-encoded defects of mitochondrial DNA maintenance and translation, OXPHOS complex assembly and mitochondrial membrane lipids. Finally, supportive and experimental therapeutic options for these currently incurable diseases are reviewed, including liver transplantation, allogeneic haematopoietic stem cell transplantation and gene therapy.
Collapse
Affiliation(s)
- Shamima Rahman
- Mitochondrial Research Group, Clinical and Molecular Genetics Unit, UCL Institute of Child Health, 30 Guilford Street, London, WC1N 1EH, UK.
| |
Collapse
|
19
|
Navarro-Sastre A, Tort F, Garcia-Villoria J, Pons MR, Nascimento A, Colomer J, Campistol J, Yoldi ME, López-Gallardo E, Montoya J, Unceta M, Martinez MJ, Briones P, Ribes A. Mitochondrial DNA depletion syndrome: new descriptions and the use of citrate synthase as a helpful tool to better characterise the patients. Mol Genet Metab 2012; 107:409-15. [PMID: 22980518 DOI: 10.1016/j.ymgme.2012.08.018] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/24/2012] [Accepted: 08/25/2012] [Indexed: 01/21/2023]
Abstract
Mitochondrial DNA depletion syndrome (MDS) is a clinically heterogeneous group of mitochondrial disorders characterised by a quantitative reduction of the mitochondrial DNA copy number. Three main clinical forms of MDS: myopathic, encephalomyopathic and hepatocerebral have been defined, although patients may present with other MDS associated clinical symptoms and signs that cover a wide spectrum of onset age and disease. We studied 52 paediatric individuals suspected to have MDS. These patients have been divided into three different groups, and the appropriate MDS genes have been screened according to their clinical and biochemical phenotypes. Mutational study of DGUOK, MPV17, SUCLA2, SUCLG1 and POLG allowed us to identify 3 novel mutations (c.1048G>A and c.1049G>T in SUCLA2 and c.531+4A>T in SUCLG1) and 7 already known mutations in 10 patients (8 families). Seventeen patients presented with mtDNA depletion in liver or muscle, but the cause of mtDNA depletion still remains unknown in 8 of them. When possible, we quantified mtDNA/nDNA and CS activity in the same tissue sample, providing an additional tool for the study of MDS. The ratio (mtDNA/nDNA)/CS has shed some light in the discrepant results between the mtDNA copy number and the enzymatic respiratory chain activities of some cases.
Collapse
Affiliation(s)
- Aleix Navarro-Sastre
- Division of Inborn Errors of Metabolism, Department of Biochemistry and Molecular Genetics, Hospital Clinic, Instituto de Investigación Biomédica Pi Sunyer, 08028 Barcelona, Spain
| | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
20
|
Gaster M, Nehlin JO, Minet AD. Impaired TCA cycle flux in mitochondria in skeletal muscle from type 2 diabetic subjects: marker or maker of the diabetic phenotype? Arch Physiol Biochem 2012; 118:156-89. [PMID: 22385297 DOI: 10.3109/13813455.2012.656653] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The diabetic phenotype is complex, requiring elucidation of key initiating defects. Recent research has shown that diabetic myotubes express a primary reduced tricarboxylic acid (TCA) cycle flux. A reduced TCA cycle flux has also been shown both in insulin resistant offspring of T2D patients and exercising T2D patients in vivo. This review will discuss the latest advances in the understanding of the molecular mechanisms regulating the TCA cycle with focus on possible underlying mechanism which could explain the impaired TCA flux in insulin resistant human skeletal muscle in type 2 diabetes. A reduced TCA is both a marker and a maker of the diabetic phenotype.
Collapse
Affiliation(s)
- Michael Gaster
- Laboratory of Molecular Physiology, Department of Pathology, Odense University Hospital, Denmark.
| | | | | |
Collapse
|
21
|
Sakamoto O, Ohura T, Murayama K, Ohtake A, Harashima H, Abukawa D, Takeyama J, Haginoya K, Miyabayashi S, Kure S. Neonatal lactic acidosis with methylmalonic aciduria due to novel mutations in the SUCLG1 gene. Pediatr Int 2011; 53:921-5. [PMID: 21639866 DOI: 10.1111/j.1442-200x.2011.03412.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND Succinyl-coenzyme A ligase (SUCL) is a mitochondrial enzyme that catalyses the reversible conversion of succinyl-coenzyme A to succinate. SUCL consists of an α subunit, encoded by SUCLG1, and a β subunit, encoded by either SUCLA2 or SUCLG2. Recently, mutations in SUCLG1 or SUCLA2 have been identified in patients with infantile lactic acidosis showing elevated urinary excretion of methylmalonate, mitochondrial respiratory chain (MRC) deficiency, and mitochondrial DNA depletion. METHODS Case description of a Japanese female patient who manifested a neonatal-onset lactic acidosis with urinary excretion of methylmalonic acid. Enzymatic analyses (MRC enzyme assay and Western blotting) and direct sequencing analysis of SUCLA2 and SUCLG1 were performed. RESULTS MRC enzyme assay and Western blotting showed that MRC complex I was deficient. SUCLG1 mutation analysis showed that the patient was a compound heterozygote for disease-causing mutations (p.M14T and p.S200F). CONCLUSION For patients showing neonatal lactic acidosis and prolonged mild methylmalonic aciduria, MRC activities and mutations of SUCLG1 or SUCLA2 should be screened for.
Collapse
Affiliation(s)
- Osamu Sakamoto
- Department of Pediatrics, Tohoku University School of Medicine, Sendai, Japan.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
22
|
Biochemical analysis of the G517V POLG variant reveals wild-type like activity. Mitochondrion 2011; 11:929-34. [PMID: 21856450 DOI: 10.1016/j.mito.2011.08.003] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/09/2011] [Revised: 07/13/2011] [Accepted: 08/04/2011] [Indexed: 11/22/2022]
Abstract
The c.1550g→t mutation in the POLG gene causing the G517V substitution has been reported by many groups to be associated with a variety of mitochondrial diseases, including autosomal dominant and recessive forms of ataxia neuropathy, myopathy and microcephaly, progressive external ophthalmoplegia, diabetes, strokes, hypotonia, and epilepsy. However, the variable disease presentation and age of onset raises suspicion of its pathogenicity. Because of the varied reported associated symptoms and request from physicians to address the consequence of this mutation, we have carried out the biochemical analysis of the purified recombinant human DNA polymerase γ protein harboring the G517V substitution. These analyses revealed that the G517V mutant enzyme retained 80-90% of wild-type DNA polymerase activity, in addition to its functional interaction with the p55 accessory subunit. DNA binding by the mutant was also only slightly lower than the wild-type enzyme. Our data suggest that the G517V mutation by itself in pol γ most likely does not have a role in mitochondrial disorders.
Collapse
|
23
|
Abstract
During the last decade rapid development has occurred in defining nuclear gene mutations causing mitochondrial disease. Some of these newly defined gene mutations cause neonatal or early infantile onset of disease, often associated with severe progressive encephalomyopathy combined with other multi-organ involvement such as cardiomyopathy or hepatopathy and with early death. Findings suggesting myopathy in neonates are hypotonia, muscle weakness and wasting, and arthrogryposis. We aim to describe the clinical findings of patients with mitochondrial disease presenting with muscular manifestations in the neonatal period or in early infancy and in whom the genetic defect has been characterized. The majority of patients with neonatal onset of mitochondrial disease have mutations in nuclear genes causing dysfunction of the mitochondrial respiratory chain, leading to defective oxidative phosphorylation.
Collapse
Affiliation(s)
- Már Tulinius
- Department of Pediatrics, University of Gothenburg, The Queen Silvia Children's Hospital, S-416 85 Göteborg, Sweden.
| | | |
Collapse
|
24
|
Randolph LM, Jackson HA, Wang J, Shimada H, Sanchez-Lara PA, Wong DA, Wong LJ, Boles RG. Fatal infantile lactic acidosis and a novel homozygous mutation in the SUCLG1 gene: a mitochondrial DNA depletion disorder. Mol Genet Metab 2011; 102:149-52. [PMID: 21093335 DOI: 10.1016/j.ymgme.2010.10.014] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/02/2010] [Revised: 10/26/2010] [Accepted: 10/26/2010] [Indexed: 11/30/2022]
Abstract
Mitochondrial DNA (mtDNA) depletion syndromes are autosomal recessive conditions in which the mtDNA copy number is greatly decreased in affected tissues. The encephalomyopathic group of these syndromes comprise mutations in SUCLA2 and SUCLG1 subunits [1]. In this report, we describe a patient with fatal infantile lactic acidosis associated with mutations in the SUCLG1 gene and mtDNA depletion. Histological and enzymatic abnormalities in skeletal muscle support the diagnosis of this recently described mitochondrial disorder. This case is unique in that prenatal imaging suggested the diagnosis and that the confirmatory molecular diagnosis was established at 2 weeks of age. We describe prenatal MRI and neonatal laboratory disturbances that can point the clinician toward consideration of this diagnosis when treating infantile lactic acidosis.
Collapse
Affiliation(s)
- Linda M Randolph
- Division of Medical Genetics, Children's Hospital Los Angeles, CA 90027, USA
| | | | | | | | | | | | | | | |
Collapse
|